Rinse mushrooms thoroughly and remove stems. Trim and finely chop stems and place in a large mixing bowl. Shred the swiss cheese (or use pre-shredded swiss cheese), and add½ cup to the mixing bowl. Reserve ¼ cup of the cheese for topping.
Add the crushed Crunchmaster® Multi-Seed Crackers, sour cream, green onion, and onion salt into the mixing bowl and mix well.
Place mushroom caps top down on to a 9 x 12 –inch baking sheet. Fill each cap with the stuffing mixture from the bowl. Be sure to press the mixture firmly into each mushroom. Sprinkle with the remaining Swiss cheese.